Method for separating reaction products obtained by reaction between propylene and aqueous ammonium polysulfide



6 6 1 .l .l 3 6 y 2 NE CN um www mom RU mp? Gnmmw CWPl RmTM E ARBU2 Il HWQNW N. PTTM e .ACAF JMASd .PEU e MEROl SYEi BUF Dn O. WDA ED t; DNN OIA HA TDTD WO March l0, 1953 .n Y. m R M TA R NH .0 m n L n Nwe m a 0. J L k vV. R AB M Patented Mar- 10, 1953 if UNITED STATESy PATENT oFFlcE Martval John Paul Hartig, Gwinliurst, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Dela- Ware Application February 12, 1952, Serial No..271,143

' This invention relates to an improved process for the separation of p-ropionamide from products obtained in reaction between propylene and aqueous ammonium polysulde.

lIn the copending Naylor application, S. N. 214,840, led March 9, 1951, which is a continuation-in-part of application S. N. 185,907, filed September 20, 1950, now abandoned, it is disclosed that certain olefin-sulfur oils obtained as by-products in the formation of amides from olens and aqueous ammonium polysulde can be recycled with a further quantity of aqueous ammonium polysulde at 200 to 350 C. whereby an additional quantity of amide is produced. The present invention is concerned with methods for separating propionamide fromv reaction products obtained in the aforesaid process and in other related processes for producing amides from oieiins, ammonium polysul'de and water.

The mixed reaction products obtained in the processes hereinabove mentioned are relatively complex, and contain propylene-sulfur oils, propionie acid, propionamide, sulfur, and tarry substances. Separation of the volatile ingredients at elevated temperatures leaves behind a mixture containing free sulfur, which is a diflicult ingredient to handle under the circumstances, especially since it reacts with propionamide rapidly at temperatures above 180 C.

An object of the present invention is to provide a suitable improved' method for working up the reaction products above described. Other objects of the invention will appear hereinafter.

These objects can be accomplished in accordance with the present invention by carrying out the series of steps defined below. One of the important features of the present invention resides in passing the reactor eluent through a flasher to produce a relatively non-volatile mixture having two liquid phases, one of which comprises free liquid sulfur, followed by decanting the molten sulfur layer and recycling it to the reactor feed supply. The process of the invention is performed by mixing ammonia, hydrogen sulfide, and water, with molten sulfur, preheating the resultant mixture under super-atmospheric pressure to a temperature within the range of 100 to 200 C., injecting propylene into the pre-heated mixture, passing the resulting mixture through a reaction zone at a temperature Within the range of 220 to 300 C., under a pressure of 150 to 1000 atmospheres, removing from the reaction zone an eiiluent comprising ammonium polysuliide, water, propionamide, propionic acid, propane, and tars, flashing the said eiiuent by lowering thepressure to within the range of -100 atmospheres whereby, at a.

2 Claims. (Cl. 26o- 561) temperature of to 175 C., anoverhead vapor l stream comprising 'hydrogen sulde, propane,

ammonia and water is produced, condensing wa.-

ter and ammonia fromthe said overhead stream, preferably in a water4 scrubber; at a temperature within the range of 20 to 100 C. under a, pres-- sure within the,l range of 10 to 100 atmospheres,"-

make-up hydrogen suliide'and ammonia, to the' reactor feed, removing the bottoms reduced by the said flasher to a recycle stream evaporator operating at a totalpressure of 1 5 atmospheres at a temperature of 120 to 180 C., to produce av vapor anda two-layered liquid, conducting the liquid to. a decanter, separating therefrom, under superatmospheric pressure, a molten sulfur layer and a; crude aqueous amide layer, recycling the sulfur layer to the said reactor feed, distilling water from the said amide layer in a.y propionamide recovery still and thereafter separating propionamide from the resulting residu-e by distillation. In a particular embodiment the vapor produced in the said recycle stream evaporator is conducted to a. condenser wherein the more volatile ingredients are separated and sent to the scrubber, a, small quantity of propionamide-containing condensatebeing withdrawn and sentv to the propionamide recovery still.

The invention is illustrated further by means of the accompanying diagrarmnatic drawing. Into a mixing vessel l is introduced arnmoi'n'a,A water, and hydrogen sulfide. Moltenl sulfur is added with vigorous mixing. This mixture after thorough mechanical agitation is conducted through a pre-heater 2 which raises the temperature to about C. Liquidpropylene is pumped into the eluent from" the pre-heater 2 and the resulting mixture. -is conducted through a reactor 3 at a temperature of about 250 C. at a pressure of 700, atmospheres. The eiiluent from the reactor 3 is conducted into an adiabatic flasher 4 wherein the pressure is suddenly dropped to 200 pounds per square inch to produce a vapor stream and a liquid eiiiuent. The vapor stream contains hydrogenV sulde, Water, propane, and ammonia and only a trace of' propionamide. This stream is conducted through' a water scrubber 5 for recovery of propionic acid and ammonia, and since this scrubbfer'is operated under acidic conditions, the hydrogen sulfide (along with propane) remains largely in the vapor phase. The mixtureof hydrogen sulfide and propane from this scrubber is conducted to `acommercial unit for converting hydrogen sul 'nde to sulfur. Several suoli units are Weil `known in the art, a typical example thereof being the so-called Thylox unit which can be purchased as a package plant. If desired, the sulfur which is recovered in the sulfur recovery unit can be recycled to the reactor feed mixer hereinabove mentioned (I). The liquid eiiluent from the adiabatic iiasher is conducted into an evaporator E which produces a liquid phase and a vapor phase. The liquid phase contains, two layers, one of which is rich in sulfur, the other being rich in propionamide. The sulfur *layer is withdrawn and recycled to the reactor feed mixer l by means of a decanter 1. The amide phase is conducted to another evaporator 8. The vapor phase from the evaporator 6 is conducted to a still wherein Y a distillation residue containing amide is produced, the remainder of the mixer being conducted to the scrubber 5. The amide residue from the still 9 is also withdrawn and conducted tothe amid-e evaporator 8. The amide evaporater B produces an aqueous vapor phase and an amide phase. The aqueous vapor phase is conducted to a still l whereby a, water-oil mixture is condensed and sent to the reactor feed mixer. The non-aqueous residue is also distilled in the still I I, yielding more oils for recycling and crude amide, which is redistilled in the still l2.

The following tables show the quantities of materials processed as hereinabove described.

TABLE l Material balances t it. Coilas Reactor 197 ft. Coil as Reactor overa Balance i@ in. i. D. yr in. i. D.

in, #Ihn out, #gm .43 4. 98 1. 54 l. 74 6. 96 5. 28 l.. 2l

n TABLE 2 x Composition and split of reactor eluent obtained in flasher [200 p. s. i. g. 155a C1 Flasher Effluent Iropoi- Flasher Feed .mno Composition (R eactorh feu Emuent) Overhead Bottoms ing Over.-

i head Percent Percent Percent Percent 0.0 0.() '0.0 0.0 22. 4 19. 6 25. l 46. 2 15. 4 23. 2 6` 8 79. 0 3l. 9 53. 5 8. 2' 87. 7 7. 4 0. 05 l5. 5 0. 3 20. 5 0. 8 42. 2 2. l l. 0 0. 0 2.15 0. 0 1.4 2. 75 (l. 0 100. 0 (82. 5#) 52. 5 (43. 2#) 47. 5 (39. 3i!) Numerous advantages have resulted from the various steps hereinabove described. '.Io obtain maximum yields it was found to be essential to Vpreheat the reactor feed prior to introduction of .propylena This virtually eliminated undesira- .ble side reactions between propy-lene and the `other components of the reactor feed, and as a. result the reaction which took place was carried out entirely at Athe optimum temperature prevail- .ing in the reaction zone. An important problem the. elimination or the ree tion. between 110i u f sulfur and propionamide. This was accordplished by means of the adiabatic flasher, and by evaporating the eilluent from this flasher at a.

operation without the necessity for frequent shut-downs to remove from the reactor or the recovery system tarry products or other undesirable ingredients of the various liquid and vapor streams.

Having now described our invention, it will be understood that various modifications may be resorted to within the scope of the invention as dened by the appended claims.

Iclaim:

1. In a process for the synthesis of propionamide the steps which comprise admixing ammonia, hydrogen sulfide, and water with molten sulfur, preheating the resultant mixture to a temperature within the range of to 200 C., injecting propylene into the said preheated mixture, passing the resulting mixture through a. reaction zone at a temperature of 220 to 300 C. under a pressure of 150 to 1000 atmospheres, removing from the reaction zone an effluent comprising ammonium polysulde, propionamide, propionic acid, propane, and tars, iiashing the said eilluent to a pressure within the range of 1,0 to 100 atmospheres, whereby an overhead vapor stream comprising hydrogen sulfide, propane, ammonia, and water is produced, cooling the said overhead stream to produce a condensate and another overhead vapor stream at a temperature of 20 to 100 C. under a pressure of 10 to 100 atmospheres, said condensate comprising water and ammonia, the latter vapor stream comprising hydrogen sulfide, water, and propane, conducting the latter stream to a sulfur recovery unit for converting hydrogen sulde to sulfur, returning the thus recovered sulfur in molten form to the reactor feed mixer, returning also the said condensate with make-up hydrogen sulfide and ammonia to the reactor feed mixer, removing the bottoms produced by the iiasher to a so-called recycle stream evaporator operating at a total pressure of 1-5 atmospheres at a temperature of -180 C. to produce a vapor and a two-layered liquid, conducting the liquid to a decanter, separating therefrom under superatmospheric pressure a molten sulfur layer and a crude aqueous amide layer, recycling the sulfur layer to the reactor feed, distilling water from the said amide layer, and thereafter separating refined propionamide from the resulting residue by distillation.

Y 2. Process of claim 1 wherein the vapor produced in the recycle stream evaporator is conducted to a condenser wherein the more volatile .ingredients are separated and sent to the sulfur recovery system, the less voltatile ingredients being forwarded to the rened propionamide recovery system.

MARTVAL JOHN PAUL HARTIG.

- N o references cited. 

1. IN A PROCESS FOR THE SYNTHESIS OF PROPIONAMIDE THE STEPS WHICH COMPRISE ADMIXING AMMONIA, HYDROGEN SULFIDE, AND WATER WITH MOLTEN SULFUR, PREHEATING THE RESULTANT MIXTURE TO A TEMPERATURE WITHIN THE RANGE OF 100* TO 200* C., INJECTING PROPYLENE INTO THE SAID PREHEATED MIXTURE, PASSING THE RESULTING MIXTURE THROUGH A REACTION ZONE AT A TEMPERATURE OF 220* TO 300* C. UNDER A PRESSURE OF 150 TO 1000 ATMOSPHERES, REMOVING FROM THE REACTION ZONE AN EFFLUENT COMPRISING AMMONIUM POLYSULFIDE, PROPIONAMIDE, PROPIONIC ACID, PROPANE, AND TARS, FLASHING THE SAID EFFLUENT TO A PRESSURE WITHIN THE RANGE OF 10 TO 100 ATMOSPHERES, WHEREBY AN OVERHEAD VAPOR STREAM COMPRISING HYDROGEN SULFIDE, PROPANE, AMMONIA, AND WATER IS PRODUCED, COOLING THE SAID OVERHEAD STREAM TO PRODUCE AN CONDENSATE AND ANOTHER OVERHEAD VAPOR STREAM AT A TEMPERATURE OF 20* TO 100* C. UNDER A PRESSURE OF 10 TO 100 ATMOSPHERES, SAID CONDENSATE COMPRISING WATER AND AMMONIA, THE LATTER VAPOR STREAM COMPRISING HYDROGEN SULFIDE, WATER, AND PROPANE, CONDUCTING THE LATTER STREAM TO A SULFUR RECOVERY UNIT FOR CONVERTING HYDROGEN SULFIDE TO SULFUR, RETURNING THE THUS RECOVERED SULFUR IN MOLTEN FORM TO THE REACTOR FEED MIXER, RETURNING ALSO THE SAID CONDENSATE WITH MAKE-UP HYDROGEN SULFIDE AND AMMONIA TO THE REACTOR FEED MIXER, REMOVING THE BOTTOMS PRODUCED BY THE FLASHER TO A SO-CALLED RECYCLE STREAM EVAPORATOR OPERATING AT A TOTAL PRESSURE OF 1-5 ATMOSPHERES AT A TEMPERATURE OF 120*-180* C. TO PRODUCE A VAPOR AND A TWO-LAYERED LIQUID, CONDUCTING THE LIQUID TO A DECANTER, SEPARATING THEREFROM UNDER SUPERATMOSPHERIC PRESSURE A MOLTEN SULFUR LAYER AND A CRUDE AQUEOUS AMIDE LAYER, RECYCLING THE SULFUR LAYER TO THE REACTOR FEED, DISTILLING WATER FROM THE SAID AMIDE LAYER, AND THEREAFTER SEPARATING REFINED PROPIONAMIDE FROM THE RESULTING RESIDUE BY DISTILLATION. 